1. Field of the Invention
In one embodiment, the invention relates to a particle or cell separation device that separates specific cell types such as neutrophils or stem cells or particles from bodily fluids such as platelets and other blood products such as red cells and plasma. Also encompassed are the bodily fluids which have been processed through the disclosed device, particularly compositions which are enriched in platelets and depleted in neutrophils.
2. Description of the Related Art
Several devices are now on the market that can process a small amount of peripheral blood (20-60 cc) automatically or semiautomatically into a fraction of that plasma that is rich in platelets. The material obtained from these devices is known as platelet rich plasma or platelet concentrate. This material is being used to augment bone grafting or to initiate soft tissue healing (See U.S. Pat. No. 6,811,777, which is incorporated herein by reference). The basis of this healing is likely due to the high concentration of growth factors found with platelets. It has been established, however, that some of the cells in platelet rich plasma may adversely affect healing or even cause further damage (Iba et al Circulation October 2002). Specifically, the neutrophils (a type of white blood cell also known as polymorphonuclear cells) contain a variety of powerful enzymes that can cause tissue inflammation. These may be present at levels of 1−3×109 per unit of whole blood and it is postulated by the inventor that removal of the neutrophils from the platelet rich plasma or whole blood may have significant value.
Importantly, neutrophils are also considered to be harmful in blood transfusions. Several devices already exist that attempt to filter or reduce the concentration of neutrophils prior to transfusions. Further, during cardiovascular bypass surgery when a patient's blood is pumped via a machine for a period of time, the perfusionist may attempt to filter out the neutrophils. Some evidence suggests that there is a better survival rate for patients that have these cells removed during the procedure. The reason for the increased survival is a lower rate of pulmonary complications after surgery. Presently, however, these filters only work incompletely and are not functional for small volumes of blood. A recent experiment involving platelet rich plasma revealed a 96% reduction in total platelet concentration when using a commercially available neutrophil reduction filter. Sixty percent of the volume (3 out of 5 cc) was also trapped in the filter (Mishra, data on file 2003). Clearly, this filter would not be helpful for specifically reducing neutrophils in platelet rich plasma. What is needed is a device that is effective in separating out neutrophils for both small and large volumes of blood while maintaining the platelet concentration. Presently, this device does not exist. Also, no available device mimics the body's own ability to filter neutrophils. This leads to the concept behind a new physiologic neutrophil separation device.